Cannondale Topstone rocking rear wheel

[LJR69]

I have Topstone 105 Carbon and when I apply the rear brake while stationary I can rock the rear wheel to-and-fro by a small amount (unlike the front wheel which is rock solid and doesn't move at all). I've had the bike just 3 weeks and only done around 100 miles on it. I'm cycling again for the first time in 37 years and so obviously tech and bike engineering has moved on considerably and so I don't know whether this is some kind of 'floating hub' or whatever

Is this normal?

 

[si_c]

Nope, not normal. Wheel needs the bearing preload fixing. Did you buy the bike from a shop or online?

 

[Paulus]

Is there any movement of the wheel without the brake applied, ie. sideways or vertical?
I would have a look to see if the brake caliper bolts are correctly tightened onto the seat/chain stays.

 

[Sharky]

Rim brakes or disc brakes?

 

[fossyant]

Check the brake caliper isn't loose as well. If you can rock it side to side with a 'clunk' then it's likely the bearings

 

[LJR69]

Thanks for the help!

@si_c Yeah, I didn't think it was right. I purchased from Pedal On in Tadley. Great shop and I've emailed them this morning too
@Sharky It's hydraulic disc brakes (sorry, should have mentioned)
@Paulus @fossyant - I can't rock the wheel sideways or vertically at all. I just checked the calliper and it looks like it's mounted okay (from what I can tell) and it itself can't be moved and rocked.

Here's a quick video I just took of it (pls excuse the dirt which I picked up on yesterday's ride - being washed after work today )

View: https://youtu.be/dudPSuLvElI

 

[Cycleops]

If it’s back and forth rather than side to side it’s probably the freehub, return it for a fix.